Expander and heat pump using the expander

ABSTRACT

An expander of the invention includes: n-number of rotary type fluid mechanisms (where n is an integer equal to or greater than 2), a first suction port ( 41   b ) for sucking a working fluid into a suction-side space ( 55   a ) of a first fluid mechanism ( 41 ), a communication port ( 43   a ) connecting a discharge-side space ( 55   b ) of a k-th fluid mechanism (where k is an integer from 1 to n−1) and a (k+1)-th suction-side space ( 56   a ) to form a single space, and a discharge port ( 51   a ) for discharging the working fluid from the discharge-side space of an n-th fluid mechanism. The expander further includes a second suction port ( 72   f ) being capable of changing its connecting position to the suction-side space ( 55   a ) of the first fluid mechanism ( 41 ), for sucking the working fluid into the suction-side space ( 55   a ).

TECHNICAL FIELD

The present invention relates to an expander applied to a refrigerationcycle apparatus (heat pump), and more particularly to a heat pump usingthe expander.

BACKGROUND ART

A power recovery type refrigeration cycle in which the energy ofexpansion of a working fluid (refrigerant) is recovered by an expanderand the recovered energy is made use of as a part of the work of acompressor has been proposed. A refrigeration cycle that employs a fluidmachine in which an expander and a compressor are coupled to each otherby a shaft (hereinafter also referred to as an “expander-compressorunit”) has been known as such a refrigeration cycle. (See JP2001-116371A).

Hereinbelow, the refrigeration cycle employing the expander-compressorunit is described.

FIG. 20 shows a refrigeration cycle using the conventionalexpander-compressor unit. In this refrigeration cycle, a main circuit 8for a working fluid (refrigerant) is constituted by a compressor 1, agas cooler (radiator) 2, an expander 3, and an evaporator 4. Thecompressor 1, the expander 3, and a rotation motor 6 are coupled to eachother by a shaft 7 to form an expander-compressor unit. The refrigerantcircuit is provided with a sub-circuit 9 in addition to the main circuit8. The sub-circuit 9 branches from the main circuit 8 at the outlet sideof the gas cooler 2 and merges with the main circuit 8 at the inlet sideof the evaporator 4. The working fluid that passes through the maincircuit 8 is expanded at the expander 3, and the working fluid thatpasses through the sub-circuit 9 is expanded by an expansion valve 5.

The working fluid is compressed in the compressor 1 to convert from alow temperature, low pressure state to a high temperature, high pressurestate, and thereafter is cooled in the gas cooler 2 to convert to a lowtemperature, high pressure state. Then, the working fluid is expanded inthe expander 3 or the expansion valve 5 to a low temperature, lowpressure state (gas-liquid two phase) and is heated at the evaporator 4to return to a low temperature, low pressure state (vapor phase). Theexpander 3 recovers the energy of expansion of the working fluid andconverts it into rotation energy for the shaft 7. This rotation energyis utilized as a part of the work for driving the compressor 1. As aresult, the power driving the rotation motor 6 can be reduced.

Here, the operation of the refrigeration cycle when the expansion valve5 is fully closed and the mass flow rate of the working fluid in thesub-circuit 9 is made zero will be described below.

The volume flow rate of the working fluid on the inlet side of thecompressor 1 and that of the expander 3 are represented as (Vcs×N) and(Ves×N), respectively, wherein the suction volume of the compressor 1 isdenoted as Vcs, the suction volume of the expander 3 is denoted as Ves,and the rotation speed of the shaft 7 is denoted as N. Since the massflow rate of the working fluid in the sub-circuit 9 is zero, the massflow rate in the compressor 1 and the mass flow rate in the expander 3are equal to each other. Where the mass flow rate is denoted as G, thedensity of the working fluid on the inlet side of the compressor 1 andthe density of the working fluid on the inlet side of the expander 3 arerepresented as {G/(Vcs×N)} and {G/(Ves×N)}, respectively, from theratios of the respective volume flow rates to mass flow rates. Fromthese formulae, the ratio of the density of the working fluid on theinlet side of the expander 3 to the density of the working fluid on theinlet side of the compressor 1 can be represented as{G/(Vcs×N)}/{G/(Ves×N)}, and thus (Ves/Vcs), which means that the ratiois constant.

FIG. 21 shows a Mollier diagram of the refrigeration cycle. In thediagram, the compression process in the compressor 1 corresponds to theline AB, the heat radiation process in the gas cooler 2 corresponds tothe line BC, the expansion process in the expander 3 corresponds to theline CD, and the evaporation process in the evaporator 4 corresponds tothe line DA. The density ratio of the working fluid at point A on theinlet side of the compressor 1 and that at point C on the inlet side ofthe expander 3 is constant, (Ves/Vcs), so the density ρ_(c) at point Ccan be represented as (Vcs/Ves)ρ₀, where the density of the workingfluid at point A is ρ₀. Assuming that the density at point A isconstant, increasing the pressure at point C means a shift from point Cto point C′ on the line ρ_(c)=(Vcs/Ves)ρ₀. That is, it is impossible toshift the process from point C to point C″, at which only the pressureis increased along the isothermal line (T=T_(c)). Thus, therefrigeration cycle is hindered from being controlled freely. In arefrigeration cycle, there is an optimal high pressure at which thecoefficient of performance (COP) becomes maximum at a certain heatsource temperature (for example, see JP 2002-81766 A). Therefore, therefrigeration cycle cannot be operated efficiently if the temperatureand the pressure cannot be controlled freely.

The constraint of the constant ratio between the density on the inletside of the compressor 1 and the density on the inlet side of theexpander 3 is due to the fact that the mass flow rate in the compressor1 and that in the expander 3 are equal to each other and also the ratioof the volume flow rates is constant. This constraint can be avoided byallowing a portion of the working fluid circulating in the refrigerantcircuit to flow through the sub-circuit 9 by opening the expansion valve5 (see JP 2001-116371 A).

In order to avoid the constraint of the constant density ratio in thepower recovery-type heat pump employing the conventionalexpander-compressor unit, which results from the fact that thecompressor and the expander rotate at the same rotation speed, it isnecessary to allow the working fluid to flow in the sub-circuit providedwith an expansion valve as well as to the main circuit provided with anexpander. In this configuration, however, the energy of expansion of theworking fluid that passes through the sub-circuit cannot be recovered.

The problem of the inefficiency in recovering the energy of expansion ofthe working fluid is noticeable in the case of using anexpander-compressor unit, but the problem also arises in the case ofusing a separate-type expander, which is not coupled to a compressor bya shaft. In the case of using a separate-type expander, the energy ofexpansion of the working fluid is recovered by a power generatorconnected to the expander. Since the power generation efficiency of thepower generator becomes poorer when the rotation speed is more distantfrom the rated rotation speed, it is desirable that the power generatorbe operated at a speed in the vicinity of the rated rotation speed. In arefrigeration cycle, however, the circulation amount and the density ofthe working fluid change depending on the operation conditions, so it isdifficult to operate the power generator only in the vicinity of therated rotation speed. Thus, even in the separate-type expander,achieving efficient recovery of the energy of expansion of the workingfluid is not easy.

DISCLOSURE OF THE INVENTION

The present invention has been accomplished in view of the foregoingcircumstances, and it is an object of the invention to provide anexpander capable of recovering the energy of expansion of the workingfluid efficiently. It is another object of the present invention toprovide a heat pump using the expander.

Accordingly, the present invention provides an expander including:

n-number of rotary type expansion mechanisms (where “n” is an integerequal to or greater than 2) each having a cylinder, a shaft with aneccentric portion, a piston fitted to the eccentric portion and rotatingeccentrically in the cylinder, and a partition member partitioning aspace between the cylinder and the piston into a suction-side space anda discharge-side space;

a first suction port for sucking a working fluid into the suction-sidespace of the first expansion mechanism;

a communication port connecting the discharge-side space of the k-thexpansion mechanism (where “k” is an integer from 1 to n−1) and thesuction-side space of the (k+1)-th expansion mechanism to form a singlespace;

a discharge port for discharging the working fluid from thedischarge-side space of the n-th expansion mechanism; and

a second suction port for sucking the working fluid into thesuction-side space of the first expansion mechanism, the second suctionport being capable of changing its connecting position to thesuction-side space of the first expansion mechanism.

The present invention also provides an expander-compressor unitincluding: an expander section having an expander according to thepresent invention; and a compressor section integrally coupled to theexpander section by the shaft.

The present invention also provides a heat pump including the expanderaccording to the present invention or the expander-integrated fluidmachine.

According to the expander of the present invention, it is possible toadjust the timing for shifting from the suction process for the workingfluid to the expansion process for the working fluid by changing theconnection position at which the suction-side space of the firstexpansion mechanism and the second suction port. Specifically, it ispossible to control the ratio of the time length for which the expansionprocess is performed to the time length for which the suction process isperformed. As a result, according to the present invention, it becomespossible to change the foregoing ratio (Ves/Vcs), and for example, it ispossible to avoid the constraint of constant density ratio in arefrigeration cycle employing an expander-compressor unit. Therefore,the energy of expansion of the working fluid can be recoveredefficiently by allowing the entire working fluid to flow into theexpander without providing a sub-circuit for the working fluid.

When using the expander according to the present invention as aseparate-type expander, the rotation speed of the expander can becontrolled while at the same time maintaining the amount of the workingfluid flowing into the expander. As a result, it becomes easy to set therotation speed of the power generator connected to the expander in thevicinity of the rated rotation speed to maintain a high power generationefficiency by the power generator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view illustrating anexpander-compressor unit according to a first embodiment of the presentinvention.

FIG. 2A is a cross-sectional view of an expander section of theexpander-compressor unit shown in FIG. 1, taken along line D1-D1 of FIG.1.

FIG. 2B is a cross-sectional view of the expander section of theexpander-compressor unit shown in FIG. 1, taken along line D2-D2 of FIG.1.

FIG. 3A is a perspective partial cut-away view of a stationary portionof an upper end plate of the expander section of the expander-compressorunit shown in FIG. 1.

FIG. 3B is a perspective view of a movable portion of the upper endplate of the expander section of the expander-compressor unit shown inFIG. 1.

FIG. 3C is a perspective partial cut-away view illustrating the upperend plate in which the stationary portion and the movable portion havebeen integrated.

FIG. 4A is a partially enlarged view illustrating the cross section ofthe expander section of the expander-compressor unit of FIG. 1, takenalong line D1-D1 of FIG. 1.

FIG. 4B is a partially enlarged view illustrating the cross section ofthe expander section of the expander-compressor unit of FIG. 1, takenalong line D1-D1 of FIG. 1.

FIG. 4C is a partially enlarged view illustrating the cross section ofthe expander section of the expander-compressor unit of FIG. 1, takenalong line D1-D1 of FIG. 1.

FIG. 5A is a view illustrating the operating principle of a firstcylinder of the expander section of the expander-compressor unit shownin FIG. 1.

FIG. 5B is a view illustrating the operating principle of a secondcylinder of the expander section of the expander-compressor unit shownin FIG. 1.

FIG. 6A is a chart illustrating the relationship between the rotationangle of the shaft and the process in the working chamber, according tothe expander section of the expander-compressor unit shown in FIG. 1.

FIG. 6B is a chart illustrating the relationship between the rotationangle of the shaft and the volumetric capacity of the working chamber,according to the expander section of the expander-compressor unit shownin FIG. 1.

FIG. 7 is a Mollier diagram illustrating the refrigeration cycle usingthe expander-compressor unit shown in FIG. 1.

FIG. 8 is a P-V diagram illustrating the relationship between thepressure and the volumetric capacity of the working chamber, accordingto the expander section of the expander-compressor unit shown in FIG. 1.

FIG. 9A is a configuration diagram illustrating a heat pump employing anexpander-compressor unit.

FIG. 9B is a configuration diagram illustrating a heat pump employing aseparate-type expander.

FIG. 10 is a graph illustrating an example of the relationship betweenthe efficiency of a power generator and the rotation speed of the powergenerator.

FIG. 11 is a vertical cross-sectional view illustrating an expanderaccording to a second embodiment of the present invention.

FIG. 12A is a cross-sectional view of the expander shown in FIG. 11,taken along line D3-D3 of FIG. 11.

FIG. 12B is a cross-sectional view of the expander shown in FIG. 11,taken along line D4-D4 of FIG. 11.

FIG. 13 is a configuration diagram illustrating a heat pump furnishedwith a pressure regulator and the expander shown in FIG. 11.

FIG. 14 is a horizontal cross-sectional view illustrating a modifiedexample of an actuator.

FIG. 15 is a configuration diagram illustrating a modified example ofthe pressure regulator.

FIG. 16A is a configuration diagram illustrating another modifiedexample of the pressure regulator.

FIG. 16B is a block diagram illustrating an example in which a pressuresensor is provided for the pressure regulator shown in FIG. 16A.

FIG. 17 is a vertical cross-sectional view illustrating anexpander-compressor unit according to a third embodiment of the presentinvention.

FIG. 18 is a plan view illustrating a rotary actuator.

FIG. 19 is a cross-sectional view of the rotary actuator of FIG. 18,taken along line D5-D5 of FIG. 18.

FIG. 20 is a configuration diagram illustrating a heat pump employing aconventional expander-compressor unit.

FIG. 21 is a Mollier diagram illustrating the refrigeration cycle usingthe heat pump employing the conventional expander-compressor unit.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, preferred embodiments of the present invention aredescribed with reference to the drawings.

First Embodiment

FIG. 1 is a vertical cross-sectional view illustrating anexpander-compressor unit according to a first embodiment of the presentinvention. FIG. 2A is a horizontal cross-sectional view of an expandersection of the expander-compressor unit shown in FIG. 1, taken alongline D1-D1 of FIG. 1. FIG. 2B is a horizontal cross-sectional view ofthe expander section of the expander-compressor unit, taken along lineD2-D2. FIG. 3A is a perspective partial cut-away view of a stationaryportion of an upper end plate of the expander section. FIG. 3B is aperspective view of a movable portion of the upper end plate. FIG. 3C isa perspective partial cut-away view illustrating the upper end plate inwhich the stationary portion and the movable portion have beenintegrated.

An expander-compressor unit 100 according to the present embodimentincludes a closed casing 11, a scroll type compressor section 20disposed in an upper portion of the closed casing, a two-stage rotaryexpander section 40 disposed in a lower portion of the closed casing, arotation motor 12 disposed between the compressor section 20 and theexpander section 40 and having a rotor 12 a and a stator 12 b, and ashaft 13 for coupling the compressor section 20, the expander section40, and the rotation motor 12 to one another. The shaft 13 may be formedof a plurality of portions joined uniaxially.

The scroll type compressor section 20 has a stationary scroll 21, anorbiting scroll 22, an Oldham ring 23, a bearing member 24, a muffler(silencer) 25, a suction pipe 26, and a discharge pipe 27. The orbitingscroll 22 is fitted to an eccentric shaft 13 a of the shaft 13 and itsself rotation is restrained by the Oldham ring 23. The orbiting scroll22, which has a vortex-shaped lap 22 a meshing with a lap 21 a of thestationary scroll 21, scrolls in association with the rotation of theshaft 13. A crescent-shaped working chamber 28 formed between the laps21 a and 22 a moves from outside to inside so as to reduce itsvolumetric capacity, thereby compressing the working fluid sucked fromthe suction pipe 26. The compressed working fluid passes through adischarge port 21 b provided at the center of the stationary scroll 21,an internal space 25 a of the muffler 25, and a flow passage 29penetrating through the stationary scroll 21 and the bearing member 24,in that order. The working fluid is then discharged to an internal space11 a of the closed casing 11. While the working fluid discharged to theinternal space 11 a is remaining in the internal space 11 a, thelubricating oil mixed in the working fluid is separated from the workingfluid by gravitational force or centrifugal force, and thereafter, theworking fluid is discharged from the discharge pipe 27 to therefrigeration cycle.

The two-stage rotary expander section 40 includes a first cylinder 41, asecond cylinder 42 having a greater thickness than the first cylinder41, and an intermediate plate 43 for separating these cylinders 41 and42. The first cylinder 41 and the second cylinder 42 are disposedconcentrically with each other. The expander section 40 further includesa first piston 44, a first vane 46, a first spring 48, a second piston45, a second vane 47, and a second spring 49. The first piston 44 isfitted to an eccentric portion 13 b of the shaft 13 to perform eccentricrotational motion in the first cylinder 41. The first vane 46 isretained reciprocably in a vane groove of the first cylinder 41 and isin contact with the first piston 44 at one end. The first spring 48 isin contact with the other end of the first vane 46 and pushes the firstvane 46 toward the first piston 44. The second piston 45 is fitted to aneccentric portion 13 c of the shaft 13 to perform eccentric rotationalmotion in the second cylinder 42. The second vane 47 is retainedreciprocably in a vane groove of the second cylinder 42 and in contactwith the second piston 45 at one end. The second spring 49 is in contactwith the other and of the second vane 47 and pushes the second vane 47toward the second piston 45.

A first (first stage) expansion mechanism is constituted by the firstcylinder 41, the shaft 13, the first piston 44, and the first vane 46.Likewise, a second (second stage) expansion mechanism is constituted bythe second cylinder 42, the shaft 13, the second piston 45 and thesecond vane 47. The pistons 44, 45 and the vanes 46, 47 respectively maybe integrated with each other (what are called swing pistons).

The expander section 40 further includes an upper end plate 73 and alower end plate 51 that are disposed so as to sandwich the first andsecond cylinders 41, 42 and the intermediate plate 43. The upper endplate 73 and the intermediate plate 43 sandwiches the first cylinder 41from the top and bottom, and the intermediate plate 43 and the lower endplate 51 sandwiches the second cylinder 42 from the top and bottom.Sandwiching the first cylinder 41 and the second cylinder 42 by theupper end plate 73, the intermediate plate 43, and the lower end plate51 forms working chambers, the volumetric capacities of which varyaccording to the rotations of the pistons 44 and 45, in the firstcylinder 41 and the second cylinder 42. The upper end plate 73 and thelower end plate 51 serve as closing members for closing the cylinders 41and 42 and also function as bearing members for retaining the shaft 13rotatably, together with the bearing member 24 of the compressor section20. Like the compressor section 20, the expander section 40 is furnishedwith a muffler 52, a suction pipe 53, and a discharge pipe 54.

As illustrated in FIGS. 2A and 2B, a suction-side working chamber 55 a(first suction-side space) and a discharge-side working chamber 55 b(first discharge-side space), which are demarcated by the first piston44 and the first vane 46, are formed in the first cylinder 41. Likewise,a suction-side working chamber 56 a (second suction-side space) and adischarge-side working chamber 56 b (second discharge-side space), whichare demarcated by the second piston 45 and the second vane 47, areformed in the second cylinder 42. The total volumetric capacity of thetwo working chambers 56 a and 56 b in the second cylinder 42 is greaterthan the volumetric capacity of the two working chambers 55 a and 55 bin the first cylinder 41. The discharge-side working chamber 55 b of thefirst cylinder 41 and the suction-side working chamber 56 a of thesecond cylinder 42 are in communication with each other through acommunication port 43 a provided in the intermediate plate 43, so theycan function as a single working chamber (expansion chamber). A highpressure working fluid flows into the working chamber 55 a, andthereafter, it expands and reduces its pressure in the working chamberformed by the working chamber 55 b and the working chamber 56 a whilerotating the shaft 13.

As illustrated in FIG. 1, the upper end plate 73 has a stationaryportion 71 and a movable portion 72. As illustrated in FIG. 3A, thestationary portion 71 has a through hole 71 f for fitting the movableportion 72 therein. The through hole 71 f is surrounded by a cylindricalrecessed surface 71 a, a cylindrical recessed surface 71 b having acentral axis 70 common to the cylindrical recessed surface 71 a and asmaller inner diameter than the cylindrical recessed surface 71 a, and astepped surface 71 c connecting these cylindrical recessed surfaces 71 aand 71 b. It should be noted that when the fluid machine (i.e., theexpander-compressor unit 100) is assembled, the central axis 70 alignsthe central axis of the shaft 13.

In the stationary portion 71, an inlet passage 71 d (first inletpassage) and an inlet passage 71 e (second inlet passage), which is abranch passage from the inlet passage 71 d, are provided as the inletpassages for guiding the working fluid from the suction pipe 53 to theworking chamber 55 a. As illustrated in FIGS. 1 and 2A, an inlet passage41 a and a first suction port 41 b are provided in the first cylinder 41as the flow passages in communication with the inlet passage 71 e. Thefirst suction port 41 b is in communication with the suction-sideworking chamber 55 a in the first cylinder 41.

As illustrated in FIG. 3B, the movable portion 72 of the upper end plate73 has a through hole 72 a for retaining the shaft 13 rotatably, andincludes as its outer circumferential surfaces a cylindrical protrudingsurface 72 b abutting on the cylindrical recessed surface 71 a of thestationary portion 71, a cylindrical protruding surface 72 c abutting onthe cylindrical recessed surface 71 b of the stationary portion 71, anda stepped surface 72 g abutting on the stepped surface 71 c of thestationary portion 71 and between the cylindrical protruding surfaces 72b and 72 c. A gear 72 e formed circumferentially around the cylindricalprotruding surface 72 c is provided in the cylindrical protrudingsurface 72 c of the movable portion 72 of the upper end plate 73. Themovable portion 72 further includes a flow passage groove 72 d providedcircumferentially in the cylindrical protruding surface 72 b and asecond suction port 72 f connected to the flow passage groove 72 d. Asillustrated in FIGS. 1 and 2A, the second suction port 72 f extends fromthe flow passage groove 72 d toward the working chamber 55 a of thefirst cylinder 41 along the axis direction and is in communication withthe suction-side working chamber 55 a in the first cylinder 41.

As illustrated in FIG. 3C, the stationary portion 71 and the movableportion 72 are integrated with each other by fitting the movable portion72 into the through hole 71 f of the stationary portion 71 rotatably.The stepped surface 71 c of the stationary portion 71 and the steppedsurface 72 g of the movable portion 72 abut onto each other so as toprevent the movable portion 72 from escaping above the stationaryportion 71. The lower end face of the stationary portion 71 and thelower end face of the movable portion 72 together constitute the sameplane, and this plane constitutes the upper wall of the first cylinder41.

When the movable portion 72 is rotated, the second suction port 72 frotates with the central axis 70 as the center of rotation while keepingthe distance from the central axis 70 of the shaft 13 constant. Therotation of the movable portion 72 brings about a relative change in theposition of the second suction port 72 in the suction-side workingchamber 55 a of the first cylinder 41. That is, while the connectionposition of the first suction port 41 b and the suction-side workingchamber 55 a of the first cylinder 41 is fixed, the connection positionof the second suction port 72 f and the working chamber 55 a isvariable. As will be described later, the change in the connectionposition of the second suction port 72 f makes it possible to avoid theconstraint of constant density ratio in the expander-compressor unit.

As described with reference to FIGS. 3A, 3B, and 3C, it is recommendedthat the second suction port 72 f be provided in the end plate 73serving as a closing member for closing an end face of the firstcylinder 41, contained in the first fluid mechanism into which theworking fluid flows initially. The reason is that the second suctionport 72 f that is movable can be constructed with a simpleconfiguration. In addition, since the cylinder 41 side of the upper endplate 73 is a flat surface, it is easy to enhance the processingaccuracy even when the end plate 73 is constructed of a plurality ofcomponents.

Furthermore, as has been explained above, it is preferable that at leasta portion of the end plate 73 be made into the movable portion 72 thatcan rotate around the shaft 13 being the center of rotation, and thatthe second suction port 72 f be provided in the movable portion 72. Thereason is that a large region can be ensured for the movement of thesecond suction port 72 f.

In addition, in the present embodiment, the movable portion 72 includesthe cylindrical bearing surface (the inner circumferential surface ofthe through hole 72 a) that supports the shaft 13. Therefore, it isunnecessary to provide a bearing for supporting the shaft 13 separately,and thereby, it is possible to prevent an increase of the parts count.

The stationary portion 71 has an annular configuration and includestherein the inlet passage 71 d (first inlet passage) for supplying theworking fluid from outside of the expander section 40 to the secondsuction port 72 f provided in the movable portion 72, and the inletpassage 71 e (second inlet passage) branched from the inlet passage 71d, for supplying the working fluid to the first suction port 41 b. Tosuch a stationary portion 71, the movable portion 72 is unitedrotatably. By providing the two inlet passages 71 d and 71 e inside thestationary portion 71, the pipes for guiding the working fluid to thesecond suction port 72 f become unnecessary, which is advantageous interms of saving the available space in the closed casing 11. Moreover,since the inlet passages 71 d and 71 e are provided inside thestationary portion 71, the problem of working fluid leakage does notarise easily.

Referring back to FIG. 1, the description will proceed further. Thestationary portion 71 of the upper end plate 73 further includes a gear75 meshing with the gear 72 e of the rotating portion 72, and a rotationmotor 76 (electric actuator) for driving the gear 75. The movableportion 72 is driven by the rotation motor 76 via the gears 72 e and 75.In this way, the expander section 40 further may include drivemechanisms 75 and 76 for rotating the movable portion 72. The drivemechanisms 75 and 76 are connected to a controller (not shown) providedoutside the closed casing 11, for controlling the rotation angle of themovable portion 72. The drive mechanisms 75 and 76 receive controlsignal from the controller and rotate the movable portion 72 to controlthe connection position to the working chamber 55 a. When using astepping motor or a servomotor as the rotation motor 76, the position ofthe second suction port 72 f can be controlled with high accuracy. It isalso possible to provide a detector (e.g., an encoder) for detecting therotation angle of the movable portion 72. It is also possible to employa means other than the rotation motor 76, such as an actuator that makesuse of the pressure difference of fluid, as the driving means for themovable portion 72.

The working fluid that has flowed from the suction pipe 53 into theexpander section 40 branches into two paths from the inlet passage 71 dof the stationary portion 71 of the upper end plate 73 and flows intothe working chamber 55 a. The first path is a path that follows theinlet passage 71 d and the branch inlet passage 71 e in the stationaryportion 71, and the inlet passage 41 a and the first suction port 41 bin the first cylinder 41. The second path is a path that follows theinlet passage 71 d in the stationary portion 71, the flow passage groove72 d and the second suction port 72 f in the movable portion 72. Thus,in the expander section 40, the working fluid is supplied from thesuction pipe 53 to the working chamber 55 a through the first suctionport 41 b, whose connection position to the working chamber 55 a isfixed, and the second suction port 72 f, whose connection position tothe working chamber 55 a is variable. In these two paths, it isunnecessary to provide a flow rate control mechanism that can be openedand closed such as a solenoid valve or a differential pressure valve.

The working fluid that has been sucked into the first cylinder 41 runsthrough the second cylinder 42, then passes through the discharge port51 a provided in the lower end plate 51, an internal space 52 a of themuffler 52, a flow passage 57 extending through the first and secondcylinders 41 and 42 in that order, and then is discharged from thedischarge pipe 54 to the refrigeration cycle. It should be noted thatthe discharge port 51 a may be provided in the second cylinder 42.

As illustrated in FIG. 2B, a discharge valve 74 is installed at thedischarge port 51 a provided in the lower end plate 51. The dischargevalve 74 is made of, for example, a metal thin plate and is disposed soas to close the discharge port 51 a from the internal space 52 a side ofthe muffler 52. The discharge valve 74 is a differential pressure valvethat opens when the pressure in the upstream side (i.e., the workingchamber 56 b side of the discharge-side of the second cylinder 42)becomes higher than the pressure in the downstream side (i.e., theinternal space 52 a side of the muffler 52). The discharge valve 74 hasthe function of preventing overexpansion of the working fluid in theexpander section 40.

FIGS. 4A, 4B, and 4C illustrate the positions of the first suction port41 b and the second suction port 72 f. The position of the secondsuction port 72 f is regulated at 20° (FIG. 4A), 90° (FIG. 4B), and 180°(FIG. 4C), represented by angle φ with respect to the position of thefirst vane 46 with the shaft 13 being the center. The angle φ is, moreprecisely, an angle formed by a first linear line 80 connecting thecentral axis 70 of the shaft 13 with the contact point between the firstvane 46 and the first piston 44, and a second linear line 90 connectingthe second suction port 72 f and the central axis 70 of the shaft 13,when the first linear line 80 is rotated in the direction of rotation(the clockwise direction in the example shown in the figure) to thesecond linear line 90, taking the central axis 70 of the shaft 13 as thecenter of rotation. According to this manner of representation, thefirst suction port 41 b is fixed at the 20° position in the exampleshown in the figures. The discharge port 51 a is fixed at the 340°position in the second cylinder 42, according to the same manner ofrepresentation. In contrast, the position of the second suction port 72f can be set freely from 0° to 360°.

FIG. 5A shows a view illustrating the operating principle of the firstcylinder 41 when the angle φ of the second suction port 72 f is 90°, andFIG. 5B shows a view illustrating the operating principle of the secondcylinder 42, which corresponds to the foregoing. Here, the rotationangle θ of the shaft 13 is represented as 0° when the contact pointbetween the first cylinder 41 and the first piston 44 is positioned atthe first vane 46, that is, what is called at the top dead center, andthe direction of rotation of the shaft 13, i.e., the clockwise directionis represented as the forward direction.

After θ=20°, the working fluid flows from the first suction port 41 binto the working chamber 55 a, which is generated after θ=0°. Afterθ=90°, the working fluid flows through the first suction port 41 b andthe second suction port 72 f into the working chamber 55 a. Afterθ=360°, the working chamber 55 a is turned into the working chamber 55 band is brought into communication with the working chamber 56 a of thesecond cylinder 42 through the communication port 43 a. As the shaft 13rotates further, the contact point between the first cylinder 41 and thefirst piston 44 passes the first suction port 41 b when θ=380° (notshown), breaking the communication between the working chamber 55 b andthe first suction port 41 b. In the conventional two-stage rotaryexpander section, the suction process for the working fluid finishes atthis point.

In contrast, because the second suction port 72 f is provided in theexpander section 40 of the present embodiment, the inflow of the workingfluid from the second suction port 72 f continues even after the angle θreaches θ=380°. In this expander section 40, the suction process for theworking fluid finishes when the angle θ reaches θ=450°, at the pointwhere the contact point between the first cylinder 41 and the firstpiston 44 passes the second suction port 72 f and where thecommunication between the working chamber 55 b and the second suctionport 72 f is broken.

When the suction process is completed, an expansion process for theworking fluid is started. As the shaft 13 rotates further, thevolumetric capacity of the working chamber 55 b reduces, but thevolumetric capacity of the working chamber 56 a increases at a greaterrate because the second cylinder 42 is axially higher and therefore hasa greater volumetric capacity than the first cylinder 41. As a result,as the shaft 13 rotates, the total of the volumetric capacities of theworking chamber 55 b and the working chamber 56 a increases, and theworking fluid expands. When the angle θ reaches θ=700° (not shown), thecontact point between the second cylinder 42 and the second piston 45passes the discharge port 51 a, bringing the working chamber 56 a intocommunication with the discharge port 51 a. The expansion processfinishes at this point.

When the expansion process is completed, a discharge process for theworking fluid is started. When θ=720°, the working chamber 55 bdisappears, and the working chamber 56 a changes into the workingchamber 56 b. As the shaft 13 rotates further, the volumetric capacityof the working chamber 56 b reduces, and the working fluid is dischargedfrom the discharge port 51 a. When θ=1080°, the working chamber 56 bdisappears, and the discharge process finishes.

FIG. 6A illustrates the relationship between the rotation angles θ ofthe shaft 13 and the shifting points of the processes from the suctionto the discharge in the cases that the angle φ of the second suctionport 72 f is 20°, 90°, and 180°. As is clear from the foregoingdescription, the rotation angle θ of the shaft 13 at which the suctionprocess finishes is an angle at which the contact point between thefirst cylinder 41 and the first piston 44 passes the second suction port72 f for the second time. This angle can be represented as θ=(360+φ).Accordingly, as the angle φ of the second suction port 72 f increases,the timing for shifting from the suction process to the expansionprocess delays, so the suction process becomes longer while theexpansion process becomes shorter. In other words, the ratio of the timelength for which the expansion process is performed to the time lengthfor which the suction process is performed becomes smaller.

FIG. 6B illustrates the relationship between the rotation angle θ of theshaft 13 and the volumetric capacity of the working chamber. As theworking fluid moves through the working chamber 55 a, the workingchamber 55 b, the working chamber 56 a, and the working chamber 56 b inthat order, the volumetric capacity of the working chamber changes in asine wave-like curve during that process. Shown on the vertical axis ofthe graph are the suction volume Vesφ, which represents the volumetriccapacity of the working chamber at the end of the suction process, foreach of the cases that the angle φ of the second suction port 72 f is20°, 90°, and 180°, and the discharge volume Ved, which represents thevolumetric capacity of the working chamber at the start of the dischargeprocess. As the angle φ increases, the suction volume Vesφ accordinglyincreases, but the discharge volume Ved is constant irrespective of theangle φ.

As described above, in the present embodiment, the suction volume Vesφ,the volumetric capacity of the working chamber 55 a, 55 b, 56 a and 56 bat the end of the suction process, is made variable by providing thesecond suction port 72 f that is movable, in addition to the firstsuction port 41 b provided in the conventional two-stage rotary expandersection 40. This makes it possible to control the density ratio(Vcs/Vesφ) of the working fluid on the inlet side of the compressorsection 20 and that of the expander section 40.

FIG. 7 illustrates a Mollier diagram of the refrigeration cycleemploying the expander-compressor unit of the present embodiment. Sincethe density ratio can be varied, point C, which corresponds to the stateon the inlet side of the two-stage rotary expander section 40, can beshifted to point C′ or point C″ by changing only the pressure along theisothermal line (T=35° C. in the example shown in the figure). Thus, thetemperature and pressure on the inlet side of the two-stage rotaryexpander section 40 can be controlled freely. As a result, it becomespossible to operate the refrigeration cycle with a high efficiency thathas been impossible with the refrigeration cycle employing theconventional expander-compressor unit.

Particularly when the second suction port 72 f is formed in the movableportion 72 that is rotatable with the axis of the shaft 13 being thecenter of rotation and the angle φ is made adjustable from 0° to 360°,as in the present embodiment, the range of the controlling becomes wideand therefore a highly efficient refrigeration cycle can be achievedeasily.

Next, the effect obtained by providing the discharge valve 74 for thedischarge port 51 a will be described below. FIG. 8 illustrates therelationship (P-V diagram) between the pressure and the volumetriccapacity of the working chamber. The subscripts φ for the symbols in thediagram denote angles φ of the second suction port 72 f. Point Pφdenotes the start of an expansion process, point Sφ denotes the end ofan expansion process, and point T denotes the start of a dischargeprocess. It should be noted that an inflection point Qφ originating froma phase change is shown in the middle of each expansion process sincethe refrigeration cycle using carbon dioxide as the working fluid isassumed.

As the suction volume Vesφ becomes greater in association with movementof the second suction port 72 f, the volumetric capacity ratio(=Ved/Vesφ) before and after the expansion process becomes smaller andthe pressure Sφ at the end of the expansion process becomes higher,because the discharge volume Ved is constant. For this reason, when, forexample, the angle φ of the second suction port 72 f is controlled inthe range of from 20° to 180°, it is desirable that the expander section40 be designed in such a manner that the pressure S₁₈₀, which is thepressure at the end of the expansion process in the case of selectingthe maximum angle 180°, is lower than the low pressure Ped of therefrigeration cycle to prevent underexpansion. The reason is that ifunderexpansion occurs, part of the energy of the working fluidoriginating from the pressure difference cannot be recovered.

In such a design, overexpansion occurs at least in the case that theangle φ is set at 180° or less. The overexpansion refers to a phenomenonin which the pressure Pedφ becomes lower than the low pressure Ped ofthe refrigeration cycle. If the overexpansion takes place, overexpansionloss occurs in the discharge process because the working fluid needs tobe pushed out from the discharge port 51 a to the internal space 52 a ofthe muffler 52, in which the pressure is higher than that in the workingchamber 56 b. The degree of the overexpansion loss can be represented bythe area of the triangle RφSφT in FIG. 8.

When the discharge valve 74 is provided for the discharge port 51 a,however, recompression is carried out in the discharge process whenoverexpansion RφSφ occurs in the working chamber 56 b. In the dischargeprocess, the volumetric capacity of the working chamber 56 b reduces asthe shaft 13 rotates. When the discharge valve 74 is provided for thedischarge port 51 a, the discharge valve 74 does not open until thepressure of the working chamber 56 b that has been reduced byoverexpansion becomes equal to the low pressure Ped of the refrigerationcycle, and therefore the working fluid is recompressed in the workingchamber 56 b. Thus, the overexpansion loss can be prevented by providingthe discharge valve 74.

Hereinbelow, other features of the expander-compressor unit according tothe present embodiment will be described.

In the present embodiment, it is recommended that the movable portion 72of the upper end plate 73 provided with the second suction port 72 fshould be rotatable in the same direction as the direction of rotationof the shaft 13, taking the shaft 13 as its center of rotation. Thereason is that the friction force between the shaft 13 and the movableportion 72 enables the movable portion 72 to be rotated with a smallermechanical power. Thereby, the size of the rotation motor 76 may bereduced so that it can be accommodated easily in the closed casing 11.

In the present embodiment, the movable portion 72 returns to theoriginal position when it rotates 360°. The movable portion 72 needs tobe driven to rotate only in the same direction, so the controlling ofthe rotation motor 76 is easy. Moreover, the friction force between theshaft 13 and the movable portion 72 does not hinder the rotationdriving.

In the present embodiment, the suction volume Vesφ of the expandersection 40 is made variable, and thereby the compressor section 20 isallowed to have a common structure used for the refrigeration cycle thatdoes not employ an expander. The common structure may be used withoutalteration for the compressor section 20 and therefore the developmentcosts can be reduced.

When using the expander-compressor unit of the present embodiment, thesuction volume Vesφ can be adjusted according to the operationconditions while the circulation amount of the working fluid in therefrigeration cycle is being controlled by the rotation speed of thecompressor section 20 and while the expander section 40 is being rotatedat the same rotation speed as that of the compressor section 20.Therefore, it is possible that the compressor section 20 and theexpander section 40 serve different roles in controlling therefrigeration cycle, and also, the control algorithm for therefrigeration cycle using the expander-compressor unit becomes simple.

Although there is no particular limitation to the type of the workingfluid used in expander-compressor unit of the present embodiment, carbondioxide is suitable. This makes the effect of power recovery by theexpander more significant. Accordingly, when using carbon dioxide as theworking fluid, the effect of improving efficiency by avoiding a constantdensity ratio also becomes more significant.

In the present embodiment, the second suction port 72 f that is movableis provided along with the first suction port 41 b. However, two or moremovable suction ports may be provided, in which case the suction volumeVesφ is determined by the suction port disposed at the most downstreamposition. Although the expander section 40 has two stages in the presentembodiment, the same advantageous effects as described above may beobtained by providing a second suction port that is movable for thefirst stage cylinder even in the case where the expander section hasthree or more stages.

Next, FIG. 9A illustrates the configuration of a power recovery typeheat pump employing the expander-compressor unit according to thepresent embodiment. The heat pump shown in FIG. 9A includes theexpander-compressor unit 100, a gas cooler (radiator) 2, an evaporator4, and piping 88 (refrigerant pipes) connecting these components to oneanother. In the conventional example shown in FIG. 20, the sub-circuit 9connected parallel to the expander 3 is indispensable, but the heat pumpemploying the expander-compressor unit according to the presentembodiment does not require such a sub-circuit as an essential item.That said, a sub-circuit may be provided for different purposes, forexample, for the purpose of carrying out the start-up and stopping ofthe heat pump stably.

Furthermore, the expander section 40 according to the present embodimentmay be used alone; in other words, it may be used as an expanderseparate from a compressor. FIG. 9B illustrates the configuration of apower recovery type heat pump employing a separate-type expander. Thissystem includes a compressor 81, a gas cooler (radiator) 82, an expander83, and an evaporator 84. It further includes piping 88 (refrigerantpipes) that connects the compressor 81, the gas cooler 82, the expander83, and the evaporator 84 in that order and in which the working fluidcirculates. The expander 83 contains the expander section 40, describedwith reference to FIG. 1 and so forth. In this heat pump, the energy ofexpansion of the working fluid, which is obtained by the expander 83, isconverted by a power generator 86 into electric energy, which is used aspart of the input to a rotation motor 85 for rotating the compressor 81.

FIG. 10 shows an efficiency curve for a common power generator 86. Sincethe power generator 86 is designed so that the power generationefficiency becomes highest at a predetermined rated rotation speed Nr,its power generation efficiency becomes poorer when the rotation speedis more distant from the rated rotation speed. For this reason, it isdesirable that the rotation speed of the power generator 86 be as closeas possible to the rated rotation speed Nr. In a refrigeration cycle,however, the circulation amount and the density of the working fluidvary, and therefore, an expander with a constant suction volume Ves isdifficult to operate only at a speed in the vicinity of the ratedrotation speed Nr. When the expander section 40 according to the firstembodiment is used as the expander 83, it becomes possible to controlthe rotation speed to a speed in the vicinity of the rated rotationspeed Nr by adjusting the suction volume Vesφ.

Second Embodiment

As has been mentioned in the foregoing embodiment, the position of thesecond suction port for varying the suction volume of the expander canbe varied by an actuator that makes use of pressure difference of afluid. The actuator making use of pressure difference of a fluidenhances reliability under severe conditions, such as under a hightemperature, high pressure environment. Another advantage is that theworking fluid that should be expanded by an expander can be utilized asit is for the power source of the actuator. The present embodimentdescribes a variable suction volume-type expander including such anactuator. In the present embodiment, the same components as described inthe first embodiment are designated by the same reference numerals.

FIG. 11 is a vertical cross-sectional view illustrating an expanderaccording to the second embodiment. As illustrated in FIG. 11, anexpander 303 is a rotary type expander. The expander 303 includes aclosed casing 11, a power generator 86 disposed in the closed casing 11,and an expander section 400 connected to the power generator 86. Theexpander section 400 includes a port member 412 b (movable member), ahousing 413 for accommodating the port member 412 b, and an actuator406.

The port member 412 b closes the cylinder 41 (first cylinder) of thefirst expansion mechanism and is capable of rotating independently ofthe shaft 13, taking the shaft 13 as the center of rotation. The portmember 412 b is provided with an additional second suction port 412 c.The actuator 406 is a fluid pressure actuator that makes use of thepressure difference of a fluid as its power source, and imparts arotational force with a magnitude corresponding to the pressuredifference between a high pressure fluid and a low pressure fluid to theport member 412 b. When switching the rotation angle of the port member412 b, the position of the second suction port 412 c around the centralaxis line O changes. Thereby, in the expander section 400, the timingfor shifting from the suction process to the expansion process for theworking fluid changes, and the ratio of the time length for which theexpansion process is performed to the time length for which the suctionprocess is performed accordingly changes.

It is possible to use the working fluid, which should be expanded by theexpander 303, as the high pressure fluid and the low pressure fluid,which are the power source of the actuator 406. In this way, it becomesunnecessary to prepare the fluid for operating the actuator 406separately. Moreover, a stringent sealing structure for preventingdifferent types of fluids from mixing together is also unnecessary. Themechanism for using the working fluid as the power source of theactuator 406 will be made clear in the following description.

In the present embodiment, the actuator 406, the port member 412 b, andthe cylinder 41 (first cylinder) of the first expansion mechanism aredisposed in that order and lined up concentrically, along a directionparallel to the central axis line O of the shaft 13. This arrangementmakes it possible to minimize the size increase arising from theprovision of the actuator 406 and the port member 412 b, and istherefore suitable for a small-sized expander 303.

Hereinbelow, the components of the expander 303 will be describedindividually. The power generator 86 includes a stator 86 b fixed to aside wall of the closed casing 11, and a rotor 86 a disposed inside thestator 86 b. A shaft 13 is fixed to a center portion of the rotor 86 a.The shaft 13 extends downwardly from the rotor 13 a. The shaft 13 isshared with the expander section 400.

An oil reservoir 405 for holding lubricating oil is formed in a bottomportion of the closed casing 11. The lower end of the shaft 13 isdisposed in the oil reservoir 405. An oil pump, which is not shown inthe drawings, is formed at a lower end portion of the shaft 13, and anoil supply passage, which is not shown in the drawings, is formed in theinterior and/or in the outer circumference portion of the shaft 13. Whenthe shaft 13 rotates, the lubricating oil in the oil reservoir 405 ispumped up by the oil pump and is supplied to various sliding parts inthe expander section 400 through the oil supply passage.

The basic structure of the expander section 400 and its workings forexpanding working fluid are the same as explained in the firstembodiment, and are not further elaborated on here. It should be notedthat the present embodiment differs from the first embodiment in thatthe actuator 406 and the port member 412 b for varying the position ofthe second suction port 412 c are disposed between the first thecylinder 41 and an upper end plate 424, serving as a bearing member, andin that an end face of the first the cylinder 41 is closed by the portmember 412 b.

Hereinbelow, the port member 412 b and the actuator 406 will bedescribed in detail. The port member 412 b is in a substantially diskshape and has a hole for accepting the shaft 13 in the center portion.It is disposed inside the housing 413, the outer shape of whichsubstantially corresponds with the first the cylinder 41. The innerdiameter of the housing 413 and the outer diameter of the port member412 b are approximately equal to each other, so that displacement of theport member 412 b in radial directions is restrained by the housing 413.The port member 412 b can, however, rotate smoothly in the housing 413.The second suction port 412 c is formed in the port member 412 b so asto pass through the port member 412 b vertically (axially) at a locationthat does not overlap with a piston 430 of the actuator 406. As the portmember 412 b rotates, the second suction port 412 c shifts in thedirection of rotation of the shaft 13.

FIG. 12A is a cross-sectional view of the expander shown in FIG. 11,taken along line D3-D3. As illustrated in FIG. 12A, the actuator 406includes an eccentric portion 412 a for driving the port member, apiston 430 for driving the port member, a cylinder 432 for driving theport member, a vane 433 for driving the port member, a spring 434 fordriving the port member, a suction pipe 53, and a pressure controlledpipe 435. The shaft 13 is located at a center portion of the cylinder432 for driving the port member.

In the following description, the phrase “for driving the port member”suffixed to the parts names of the actuator 406 will be omitted forbrevity.

As illustrated in FIG. 12A, the eccentric portion 412 a is off-centeredwith respect to the shaft 13 and is disposed in the cylinder 432. Thetop side of the cylinder 432 is closed by the upper end plate 424 (seeFIG. 11). The piston 430 is fitted into the eccentric portion 412 a soas to form pressure chambers 431 (431 a, 431 b) between the piston 430and the cylinder 432. The eccentric portion 412 a and the piston 430rotate (more specifically, swings eccentrically) in the cylinder 432while keeping an eccentric state with respect to the central axis line Oof the shaft 13. A through hole through which the shaft 13 extends isformed in the eccentric portion 412 a. The eccentric portion 412 a andthe shaft 13 are not joined so that they can rotate independently ofeach other.

The vane 433 is retained reciprocably in a vane groove provided in thecylinder 432 so that its leading end makes contact with the piston 430.The spring 434 pushes the vane 433 toward the piston 430.

The pressure chambers 431 a and 431 b formed in the cylinder 432 aredivided by the vane 433 into two spaces, a first pressure chamber 431 aand a second pressure chamber 431 b. A high-pressure side inlet port 450and a low-pressure side inlet port 451 also are provided in the cylinder432. The high-pressure side inlet port 450 and the low-pressure sideinlet port 451 are spaced circumferentially at a predetermined angle,and both penetrate the cylinder 432. The suction pipe 53 is connected tothe first pressure chamber 431 a via the high-pressure side inlet port450. The suction pipe 53 is for supplying a high pressure working fluidbefore expansion to the first pressure chamber 431 a. The pressurecontrolled pipe 435 is connected to the second pressure chamber 431 bvia the low-pressure side inlet port 451. The pressure controlled pipe435 is for supplying the second pressure chamber 431 b with a workingfluid having a lower pressure than that of the working fluid supplied tothe first pressure chamber 431 a. The pressure difference between thefirst pressure chamber 431 a and the second pressure chamber 431 bimparts a rotational force to the piston 430. The piston 430 that hasreceived the rotational force originating from the pressure differenceof the working fluid rotates the eccentric portion 412 a and the portmember 412 b.

Also formed in the cylinder 432 is a suction passage 437 for sucking theworking fluid into the working chamber 55 a of the first the cylinder41, which passes from the suction pipe 53 via the upper end plate 424,the cylinder 432, the housing 413, and the first cylinder 41.

In other words, the expander section 400 in the expander 303 of thepresent embodiment includes the suction passage 437 that is connected tothe first suction port 41 b formed in the first cylinder 41 and is forsending the working fluid (refrigerant) to the first cylinder 41, andthe high-pressure side inlet port 450 as a branch passage, branched fromthe suction passage 437. The high pressure chamber 431 a of the actuator406 and the high-pressure side inlet port 450 are connected to eachother, and the high pressure working fluid supplied through thehigh-pressure side inlet port 450 to the actuator 406 is utilized as thehigh pressure fluid for driving the actuator 406. Moreover, the actuator406 and the port member 412 b are disposed vertically adjacent to eachother so that one end of the second suction port 412 c provided in theport member 412 b can be connected to the high pressure chamber 431 a ofthe actuator 406. The working fluid supplied to the actuator 406 as thehigh pressure fluid is supplied through the second suction port 412 cprovided in the port member 412 b to the working chamber 55 a in thefirst cylinder 41 (see FIG. 2A).

In this way, it becomes unnecessary to prepare the fluid for operatingthe actuator 406 separately. It is unnecessary to provide a stringentsealing structure for preventing different kinds of fluids from mixingwith each other, and in addition, the problem of the changes in thecharacteristics of the refrigeration cycle caused by mixing of differentkinds of fluids does not arise. Moreover, because the working fluid usedin the expander 303 is used as the power source of the actuator 406, noenergy, such as electric power, needs to be supplied from outside. Thisis advantageous for improving the efficiency in recovering the energy ofexpansion of the working fluid.

On the inner circumferential surface of the cylinder 432, a firststopper 436 a and a second stopper 436 b protruding toward the centralaxis line O of the shaft 13 are provided circumferentially spaced apartat a predetermined angle. These stoppers 436 a and 436 b restrict themovable range (the rotation angle around the central axis line O) of thepiston 430 when it is rotated by the pressure difference (when theworking fluid (refrigerant) is carbon dioxide, the high pressure ishigher than about 10 MPa and the low pressure is about 3 MPa to 5 MPaduring a rated operation) of the working fluid. Thereby, the port member412 b is permitted to rotate only within the range of a predeterminedangle (for example, about 180°).

It should be noted that the center of rotation of the piston 430 of theactuator 406 may correspond to the center of rotation of the shaft 13.However, when the structure in which the piston 430 eccentricallyrotates is employed as in the present embodiment, the space for formingthe second suction port 412 c that penetrates the port member 412 bvertically can be ensured easily, which is also advantageous for sizereduction of the expander.

FIG. 12B is a cross-sectional view of the expander 303 shown in FIG. 11,taken along line D4-D4. As illustrated in FIG. 12B, a rotation spring439 (pushing means) is attached to the port member 412 b. It ispreferable that the rotation spring 439 be incorporated in the portmember 412 b. The rotation spring 439 is interposed between the portmember 412 b and the housing 413 (or the cylinder 432). It applieselastic force to the port member 412 b, the eccentric portion 412 a, andthe piston 430 in a predetermined direction of rotation at all times. Asillustrated in FIG. 12A, the first pressure chamber 431 a serves as thehigh-pressure side while the second pressure chamber 431 b serves as thelow-pressure side in the present embodiment. Therefore, the direction inwhich the rotation spring 439 applies elastic force is set to be thedirection in which the volumetric capacity of the first pressure chamber431 a reduces, in other words, in the direction in which the position ofthe second suction port 412 c moves closer to the first suction port 41b (see FIG. 2A). Because of the workings of the rotation spring 439, theposition of the port member 412 b can be varied continuously within themovable range determined by the stoppers 436 a and 436 b. In addition,it becomes possible to rotate the port member 412 b in both forward andreverse directions under the condition in which the working fluidsupplied to the first pressure chamber 431 a is at a high pressure andthe working fluid supplied to the second pressure chamber 431 b is at alow pressure.

Of course, in the case that the rotation spring 439 is not provided aswell, the port member 412 b can be rotated in both forward and reversedirections by reversing the magnitude relationship between the pressureof the working fluid supplied to the first pressure chamber 431 a andthe pressure of the working fluid supplied to the second pressurechamber 431 b. It is also possible to restrict the range of rotation ofthe port member 412 b by providing the stoppers 436 a and 436 b.However, in such a configuration, it is difficult to utilize the workingfluid used in the expander 303 for the power source of the actuator 406,and moreover, the structure becomes complicated. Therefore, it ispreferable that the configuration as in the present embodiment beemployed.

Moreover, with the rotation spring 439 such as described above, themagnitude of the rotational force imparted to the piston 430 is changedaccording to the position taken by the piston 430 in the cylinder 432.When the rotational force in the forward direction (or the reversedirection) that is imparted to the eccentric portion 412 a and thepiston 430 by the pressure difference between the high pressure workingfluid supplied to the first pressure chamber 431 a and the low pressureworking fluid supplied to the second pressure chamber 431 b iscounterbalanced with the repulsive force by the rotation spring 439,that is, the rotational force imparted to the port member 412 b in thereverse direction (or the forward direction), the position of the portmember 412 b is determined at a predetermined rotation angle. In thisway, it becomes possible to control the position of the port member 412b freely by adjusting the pressure difference between the working fluidsupplied to the first pressure chamber 431 a and the working fluidsupplied to the second pressure chamber 431 b of the actuator 406. Inother words, it becomes possible to adjust the second suction port 412 cto be at the optimal position according to the operation condition ofthe expander 303.

As described above, a high pressure working fluid passes through thesuction pipe 53 to the suction passage 437 and flows into the workingchamber 55 a from the first suction port 41 b provided in the firstcylinder 41 (see FIG. 2A). Apart from that passage, a high pressureworking fluid passes through the high-pressure side inlet port 450branched from the suction pipe 53 and flows into the first pressurechamber 431 a in the cylinder 432, and it passes through the secondsuction port 412 c provided in the port member 412 b and flows into theworking chamber 55 a. Since the position of the second suction port 412c changes as the port member 412 b rotates, the suction volume of theworking fluid to the first cylinder 41 changes.

In the present embodiment, the eccentric portion 412 a and the portmember 412 b are coupled or integrated with each other vertically,parallel to the central axis line O. As illustrated in FIGS. 11 and 12B,the port member 412 b is in a substantially disk shape. One of mainsurfaces of the port member 412 b closes the first cylinder 41 while theother one of main surfaces closes the cylinder 432. On the other one ofmain surfaces side, the port member 412 b is coupled (or united) withthe eccentric portion 412 a. The portion positioned distant from thefirst cylinder 41 is the eccentric portion 412 a. The portion positionednear the first cylinder 41 is the port member 412 b. In this way, thepower transfer mechanism from the actuator 406 to the port member 412 bcan be eliminated, contributing to reducing the parts count andsimplifying the structure, and a highly reliable expander 303 can beprovided. It should be noted that the eccentric portion 412 a can alsoserve the role of the piston 430, and in that case, the port member 412b can be constructed as a component integrated with the piston 430.

The positional relationship between the first suction port 41 b and thesecond suction port 412 c is as described above with reference to FIGS.4A, 4B, and 4C.

Also, the operation principles of the first cylinder 41 and the secondcylinder 42 are as described above with reference to FIGS. 5A and 5B.

The relationship between the rotation angle θ of the shaft 13 and thetime point for shifting the processes from suction to discharge is asdescribed above with reference to FIG. 6A.

The relationship between the rotation angle θ of the shaft 13 and thevolumetric capacity of the working chamber is as described above withreference to FIG. 6B.

Next, a pressure regulator for controlling the pressure of the workingfluid to be supplied to the pressure controlled pipe 435 of the actuator406 will be described below. A heat pump 300 shown in FIG. 13 includesthe compressor 81, the gas cooler 82, the expander 303 described withreference to FIG. 11, the evaporator 84, and a pressure regulator 500A.The pressure regulator 500A regulates the pressure difference between ahigh pressure fluid and a low pressure fluid to be supplied to theactuator 406 of the expander 303. By providing such a pressure regulator500A, it becomes possible to control the workings of the actuator 406from the outside of the expander 303. In the example shown in FIG. 13,the pressure regulator 500A is installed outside the expander 303, butit may be installed inside the expander 303.

The pressure regulator 500A includes a first pressure pipe 501, one endof which is connected to the suction pipe 53 of the expander 303, asecond pressure pipe 502, one end of which is connected to the pressurecontrolled pipe 435 of the expander 303, a third pressure pipe 503, oneend of which is connected to the discharge pipe 54 of the expander 303,and a hollow housing 513, to which the other ends of the pressure pipes501, 502, and 503 are connected. In other words, the outlet pipe of thegas cooler 82 is branched into the first pressure pipe 501 and thesuction pipe 53 of the expander 303. In addition, the discharge pipe 54of the expander 303 and the third pressure pipe 503 merge with eachother, forming an inlet pipe of the evaporator 84. The interior of thehousing 513 is formed into three pressure regulating chambers, a firstpressure regulating chamber 504, a second pressure regulating chamber505, and a third pressure regulating chamber 506. The first pressurepipe 501 is connected to the first pressure regulating chamber 504. Thesecond pressure pipe 502 is connected to the second pressure regulatingchamber 505. The third pressure pipe 503 is connected to the thirdpressure regulating chamber 506.

An elastic body 507 (spring) is disposed in the third pressureregulating chamber 506. A piston 508, one end of which is connected tothe elastic body 507, is disposed between the second pressure regulatingchamber 505 and the third pressure regulating chamber 506, forseparating the two pressure regulating chambers. The piston 508 can moveback and forth between the second pressure regulating chamber 505 andthe third pressure regulating chamber 506. A micro flow passage 514 forbring the second pressure regulating chamber 505 and the third pressureregulating chamber 506 in communication with each other is formed in thepiston 508. A valve 509 for adjusting the amount of the working fluidflowing between the first pressure regulating chamber 504 and the secondpressure regulating chamber 505 is provided between the two pressureregulating chambers. One end of a coupling shaft 512 is connected to thevalve 509. The other end of the coupling shaft 512 is connected to aniron core 511. A coil 510 is disposed around the iron core 511. The ironcore 511 and the coil 510 together form a plunger solenoid.

In the pressure regulator 500A, the pressure of the first pressureregulating chamber 504 is equal to the high pressure of the refrigerantcircuit, and the pressure of the third pressure regulating chamber 506is equal to the low pressure of the refrigerant circuit. The pressure ofthe second pressure regulating chamber 505 controlled by the pressureregulator 500A is supplied to the pressure controlled pipe 435 of theexpander 303 and is used for changing the suction volume of the expandersection 400.

In the configuration as shown in FIG. 13, the resilient force of theelastic body 507, the pressure resulting from the pressure differencebetween the second pressure regulating chamber 505 and the thirdpressure regulating chamber 506, and the driving force imparted by thecurrent passed through the coil 510 are applied to the coupling shaft512. The coupling shaft 512 stops at the position where these forces arebalanced. The pressure of the second pressure regulating chamber 505 canbe controlled by varying the current passed through the coil 510.

Specifically, the pressure regulator 500A acquires a portion of the highpressure working fluid to be sent to the first suction port 41 b of theexpander section 400, and decompresses the acquired working fluid tothereby produce a low pressure working fluid to be supplied to thesecond pressure chamber 431 b of the actuator 406. Then, by adjustingthe degree of decompression of the working fluid, the pressure of thesecond pressure chamber 431 b formed in the cylinder 432 for driving theport member is regulated, and the positions of the port member 412 b andthe second suction port 412 c provided in the port member 412 b arecontrolled around the central axis line O. In this way, the controlprocess of the position of the second suction port 412 c can be carriedout easily and accurately.

As described above, the heat pump 300 includes: the first pressure pipe501, having one end connected to the main pipe (the suction pipe 53) forsending the working fluid to the first suction port 41 b of the expandersection 400 and the other end connected to the pressure regulator 500A,and supplying a portion of the high pressure working fluid that is to beexpanded to the first pressure regulating chamber 504 of the pressureregulator 500A; and the second pressure pipe 502, having one endconnected to the second pressure regulating chamber 505 of the pressureregulator 500A and the other end connected to the actuator 406 (moreprecisely the pressure controlled pipe 435), and supplying the lowpressure chamber 431 b of the actuator 406 (see FIG. 14) with theworking fluid that has been decompressed to a low pressure by thepressure regulator 500A.

The workings of the pressure regulator 500 will be described. Forexample, when it is desired to increase the suction volume of theexpander 303 (the expander section 400), the current flowing through thecoil 510 should be increased. Then, the force applied to the iron core511 toward the elastic body 507 increases and compresses the elasticbody 507, and the valve 509 narrows the passage between the firstpressure regulating chamber 504 and the second pressure regulatingchamber 505. Thereby, the pressure of the second pressure regulatingchamber 505 reduces and becomes close to the pressure of the thirdpressure regulating chamber 506. Accordingly, the pressure differencebetween the pressure in the pressure controlled pipe 435 and thepressure in the suction pipe 53 increases. The piston 430 for drivingthe port member and the eccentric portion 412 a for driving the portmember rotate in a direction in which the volumetric capacity of thesecond pressure chamber 431 b decreases. The second suction port 412 carrives at, for example, the position shown in FIG. 4C. As a result, thesuction time of the expander 303 becomes longer, and the suction volumeincreases, according to the principle that has been explained withreference to FIGS. 5A and 5B.

Conversely, when it is desired to decrease the suction volume of theexpander 303 (the expander section 400), the current flowing through thecoil 510 should be decreased. Then, the force applied to the iron core511 toward the elastic body 507 decreases, so that the elastic body 507elongates, and at the same time, the valve 509 widens the passagebetween the first pressure regulating chamber 504 and the secondpressure regulating chamber 505. Thereby, the pressure of the secondpressure regulating chamber 505 increases and becomes close to thepressure of the first pressure regulating chamber 504. Accordingly, thepressure difference between the pressure in the pressure controlled pipe435 and the pressure in the suction pipe 53 reduces. The piston 430 fordriving the port member and the eccentric portion 412 a for driving theport member rotate in a direction in which the volumetric capacity ofthe second pressure chamber 431 b increases. The second suction port 412c arrives at, for example, the position shown in FIG. 4A. As a result,the suction time of the expander 303 becomes shorter, and the suctionvolume decreases, according to the principle that has been explainedwith reference to FIGS. 5A and 5B.

It is also possible to employ a pressure regulator having theconfiguration as shown in FIG. 15. First, as illustrated in FIG. 14, amicro passage 440 that bypasses the pressure controlled pipe 435 and thesuction pipe 53 is provided in an actuator 406′. As illustrated in FIG.15, a pressure regulator 500B includes a housing 515, the coil 510, theiron core 511, the coupling shaft 512, a piston 516, and the elasticbody 507 (spring). The interior of the housing 515 is partitioned intotwo pressure regulating chambers 520 and 521. A valve 509 for adjustingthe amount of the working fluid flowing between the two pressureregulating chambers 520 and 521 is provided between the two pressureregulating chambers. The coil 510 and the iron core 511 together form aplunger solenoid. The elastic body 507 pushes the valve 509 in thedirection in which it opens, via the piston 516. On the other hand, whenpassing electric current through the coil 510, the iron core 511 pushesthe valve 509 in the direction in which it closes, via the couplingshaft 512. That is, the opening of the valve 509 can be controlled bycontrolling the electric current passing through the coil 510. Thepressure of a pressure regulating chamber 521, to which the pressurecontrolled pipe 435 is connected, can be changed according to theopening of the valve 509.

It should be noted that in the examples shown in FIGS. 13 and 15, it isnecessary to keep the control pressure by causing the working fluid toflow in a small amount at all times, and therefore, the efficiency inrecovering the energy of expansion lowers inevitably. In view of this,when the control pressure is produced with the configuration as shown inFIG. 16A, it is possible to enhance the efficiency in recovering theenergy of expansion further.

A pressure regulator 500C shown in FIG. 16A includes a housing 560 inwhich the interior thereof is partitioned into three pressure regulatingchambers, a first pressure regulating chamber 561, a second pressureregulating chamber 562, and a third pressure regulating chamber 563. Thefirst pressure pipe 501 in which the working fluid before expansioncirculates is connected to the first pressure regulating chamber 561.The second pressure pipe 502, which brings the second pressureregulating chamber 562 and the second pressure chamber 431 b of theactuator 406 in the expander 303 (see FIG. 12A) into communication witheach other, is connected to the second pressure regulating chamber 562.The third pressure pipe 503 in which the working fluid after expansioncirculates is connected to the third pressure regulating chamber 563. Afirst valve 580 is disposed between the first pressure regulatingchamber 561 and the second pressure regulating chamber 562. Theopen/close operation of the first valve 580 can be controlled byactuating a plunger solenoid including a coil 570, an iron core 573, anelastic body 584 (spring), and a coupling shaft 576. A high pressureworking fluid can be sent into the second pressure regulating chamber562 by opening the first valve 580. On the other hand, a second valve581 is disposed between the second pressure regulating chamber 562 andthe third pressure regulating chamber 563. As in the case of the firstvalve 580, the open/close operation of the second valve 581 can becontrolled by a plunger solenoid including a coil 571, an iron core 574,an elastic body 585 (spring), and a coupling shaft 577. A working fluidcan be sent from the second pressure regulating chamber 562 to the thirdpressure regulating chamber 563 by opening the second valve 581. Thus,it becomes possible to produce a control pressure between the pressureof the working fluid before expansion and the pressure of the workingfluid after expansion by controlling the open/close operation of the two(a plurality of) valves 580 and 581 so that the interior of the secondpressure regulating chamber 562, and accordingly the interior of thesecond pressure chamber 431 b of the actuator 406, can be kept at theproduced control pressure. When the pressure of the second pressureregulating chamber 562 is higher than a desired pressure, the firstvalve 580 should be closed while the second valve 581 should be opened.When the pressure is lower than a desired pressure, the first valve 580should be opened while the second valve 581 should be closed.

In addition, as illustrated in the block diagram of FIG. 16B, thepressure regulator 500C may include a pressure sensor 590 for detectingthe pressure in the second pressure regulating chamber 562 and acontroller 591 for controlling the open/close operation of the valves580 and 581 based on the result detected by the pressure sensor 590. Thepressure sensor 590 may be disposed in the second pressure chamber 431 bof the actuator 406 in the expander 303. The controller 591 acquiressensor signal from the pressure sensor 590 and calculates the differencebetween the target pressure value and the current pressure value. If thecalculated difference is out of a predetermined permissible range, itcontrols the open/close operation of the first valve 580 and the secondvalve 581 so that the difference becomes smaller. Specifically, if thecurrent pressure value is smaller than the target pressure value, thesolenoid on the first valve 580 side is driven for a certain time sothat a certain amount of a high pressure working fluid flows from thefirst pressure regulating chamber 561 into the second pressureregulating chamber 562. Conversely, if the current pressure value isgreater than the target pressure value, the solenoid on the second valve581 side is driven for a certain time to move the working fluid from thesecond pressure regulating chamber 562 to the third pressure regulatingchamber 563.

By repeating such a process, the pressure of the second pressureregulating chamber 562 can be adjusted quickly and accurately to thedesired pressure. Since the solenoids (the coils 570 and 571) foropening/closing the first valve 580 and the second valve 581 do notrequire electric current at all times, it is possible to reduce powerconsumption of the pressure regulator 500C, which is advantageous forimproving the efficiency in recovering the energy of expansion of theworking fluid. Moreover, when a program that monitors the input from thepressure sensor 590 periodically is installed in the controller 591, thepressure in the second pressure regulating chamber 562 can be recoveredto a desired pressure automatically even if a pressure variation occursdue to unavoidable working fluid leakage or the like.

Third Embodiment

The features of the expander illustrated in the second embodiment may beemployed suitably for an expander-compressor unit in which an expandersection and a compressor section are integrated with each other by ashaft, as explained in the first embodiment. FIG. 17 is a verticalcross-sectional view illustrating such an expander-compressor unit.

An expander-compressor unit 700 includes a closed casing 11, a scrolltype compressor section 20 disposed in an upper portion of the closedcasing 11, a two-stage rotary expander section 400 disposed in a lowerportion of the closed casing 11, a rotation motor 12 disposed betweenthe compressor section 20 and the expander section 400, and a shaft 13commonly used for the compressor section 20, the expander section 400,and the rotation motor 12. As the rotation motor 12 drives rotation ofthe shaft 13, the compressor section 20 operates. Thisexpander-compressor unit 700 makes use of the rotational force impartedto the shaft 13 by the working fluid (refrigerant) when expanding at theexpander section 400 as auxiliary power for the compressor section 20.High energy recovery efficiency is expected because the energy ofexpansion of the working fluid is transferred directly to the compressorsection 20 without being converted to electric energy.

As described in the second embodiment, the expander section 400 includesthe port member 412 b provided with the second suction port 412 c forchanging a suction volume, and the actuator 406 for rotating the portmember 412 b to change the position. The structures and functions of theport member 412 b and the actuator 406 are the same as described in thesecond embodiment.

The basic structures and operation principle of the compressor section20 and the expander section 400 are also the same as described in thefirst embodiment.

With the expander-compressor unit 700 shown in FIG. 17, the actuator 406is driven by the pressure difference between the working fluid fed fromthe pressure controlled pipe 435 and the working fluid fed from thesuction pipe 53, and thereby the position of the port member 412 b(rotation angle around the central axis line O) can be changed. Bycontrolling the position of the port member 412 b, the suction volume ofthe expander section 400 can be controlled freely. A heat pump employingsuch an expander-compressor unit 700 makes it possible to control theflow rate of the working fluid flowing through the expander section 400freely without providing a bypass circuit, and accordingly realizes ahighly efficient heat pump system.

Fourth Embodiment

The actuator incorporated in the expander according to the secondembodiment may be employed for an expander or an expander-compressorunit suitably, but it also may be configured as a rotary actuator forother applications.

FIG. 18 is a vertical cross-sectional view illustrating a rotaryactuator according to a fourth embodiment. FIG. 19 is a cross-sectionalview taken along line D5-D5 in FIG. 18. As illustrated in FIGS. 18 and19, a rotary actuator 800 includes a cylinder 806, a shaft 801penetrating the cylinder 806, a piston 807 that swings eccentrically inthe cylinder 806 to rotate the shaft 801, and a vane 812 partitioning apressure chamber 808 formed between the cylinder 806 and the piston 807into a first pressure chamber 808 a and a second pressure chamber 808 b.

The shaft 801 has an eccentric portion 802 protruding radially outwardlyat its intermediate portion. One end of the shaft 801 penetrates anupper end plate 803 while its other end penetrates a lower end plate804. A closing member 805 is disposed below the lower end plate 804. Theupper end plate 803 and/or the closing member 805 may contain a bearingfor the shaft 801. The eccentric portion 802 of the shaft 801 isdisposed in the cylinder 806. A ring-shaped piston 807 is fitted ontothe eccentric portion 802.

The rotary actuator 800 includes the vane 812, a spring 809, a suctionpipe 810, and a pressure controlled pipe 811. The vane 812 is retainedreciprocably in a vane groove provided in the cylinder 806 so that itsleading end makes contact with the piston 807. The spring 809 pushes thevane 812 toward the piston 807. In the upper end plate 803 that closesthe top of the cylinder 806, a first inlet port 820 in communicationwith the first pressure chamber 808 a and a second inlet port 821 incommunication with the second pressure chamber 808 b are formed. Thesuction pipe 810 is connected to the first pressure chamber 808 a viathe first inlet port 820. The pressure controlled pipe 811 is connectedto the second pressure chamber 808 b via the second inlet port 821. Thepressure difference between the first fluid flowing into the firstpressure chamber 808 a and the second fluid flowing into the secondpressure chamber 808 b produces a force applied to the piston 807,rotating the eccentric portion 802 and consequently the overall shaft801. A first stopper 813 a and a second stopper 813 b are formedcircumferentially spaced at a predetermined angle on the innercircumferential surface of the cylinder 806. These stoppers 813 a and813 b restrain the range of rotation of the piston 807 when it isrotated by the pressure difference of the working fluid.

It should be noted that the elastic body for imparting a repulsive forceto the rotation of the shaft 801 is not provided in the presentembodiment, but it is possible to provide an elastic body (a rotationspring 439: see FIG. 12B) as described in the second embodiment. In thisway, it becomes possible to control the rotation angle of the shaft 801by adjusting the pressure difference between the first fluid flowinginto the first pressure chamber 808 a and the second fluid flowing intothe second pressure chamber 808 b. The first fluid and the second fluidmay be either the same or different kinds of fluids. Possible examplesof such fluids include oil in the hydraulic pressure circuit,refrigerant in the refrigerant circuit, and air in the air pressurecircuit.

INDUSTRIAL APPLICABILITY

As has been described above, the expander according to the presentinvention has great utility value since it provides an efficient meansfor recovering the energy of expansion of the working fluid in arefrigeration cycle and, in particular, achieves high efficiency in aheat pump employing an expander-compressor unit.

1. An expander comprising: n-number of rotary type expansion mechanisms(where “n” is an integer equal to or greater than 2) each having acylinder, a shaft with an eccentric portion, a piston fitted to theeccentric portion and rotating eccentrically in the cylinder, and apartition member partitioning a space between the cylinder and thepiston into a suction-side space and a discharge-side space; a firstsuction port for sucking a working fluid into the suction-side space ofthe first expansion mechanism; a communication port connecting thedischarge-side space of the k-th expansion mechanism (where “k” is aninteger from 1 to n−1) and the suction-side space of the (k+1)-thexpansion mechanism to form a single space; a discharge port fordischarging the working fluid from the discharge-side space of the n-thexpansion mechanism; and a second suction port for sucking the workingfluid into the suction-side space of the first expansion mechanism, thesecond suction port being capable of changing its connecting position tothe suction-side space of the first expansion mechanism.
 2. The expanderaccording to claim 1, further comprising: an intermediate plate disposedbetween the cylinder of the k-th expansion mechanism and the cylinder ofthe (k+1)-th expansion mechanism, for separating the cylinders, andwherein the first suction port is provided in the cylinder of the firstexpansion mechanism, the communication port is provided in theintermediate plate, and the discharge port is provided in the cylinderof the n-th expansion mechanism and/or in a closing member for closingthe cylinder of the n-th expansion mechanism.
 3. The expander accordingto claim 1, further comprising: a closing member for closing thecylinder of the first expansion mechanism at an end face thereof, andwherein the second suction port is provided in the closing member. 4.The expander according to claim 3, wherein: the closing member includesa movable portion capable of rotating, taking the shaft as the center ofrotation, and the second suction port is provided in the movableportion.
 5. The expander according to claim 4, wherein the movableportion includes a cylindrical bearing surface for supporting the shaft.6. The expander according to claim 4, further comprising a drivemechanism for rotating the movable portion.
 7. The expander according toclaim 6, wherein the drive mechanism includes an electric actuator. 8.The expander according to claim 4, wherein the closing member furtherincludes an annular stationary portion to which the movable portion isunited rotatably, the annular stationary portion having therein a firstinlet passage for supplying the working fluid from outside of theexpander to the second suction port provided in the movable portion, anda second inlet passage branched from the first inlet passage, forsupplying the working fluid to the first suction port.
 9. Anexpander-compressor unit comprising: an expander section comprising anexpander according to claim 1; and a compressor section coupledintegrally with the expander section by the shaft.
 10. A heat pumpcomprising an expander according to claim
 1. 11. A heat pump comprisingan expander-compressor unit according to claim
 9. 12. The expanderaccording to claim 1, further comprising: a movable member that closesthe cylinder of the first expansion mechanism and that is capable ofrotating independently of the shaft, taking the shaft as the center ofrotation; and an actuator imparting a rotational force having amagnitude corresponding to a pressure difference between a high pressurefluid and a low pressure fluid to the movable member, wherein the secondsuction port is provided in the movable member.
 13. The expanderaccording to claim 12, wherein the working fluid is used as the highpressure fluid and the low pressure fluid.
 14. The expander according toclaim 12, wherein the actuator, the movable member, and the firstexpansion mechanism are disposed in that order along a directionparallel to the central axis line of the shaft.
 15. The expanderaccording to claim 12, further comprising: a suction passage connectedto the first suction port, for sending the working fluid to the cylinderof the first expansion mechanism; and a branch passage branched from thesuction passage, and wherein: a high pressure chamber of the actuatorand the branch passage are connected to each other, and a high pressureworking fluid supplied to the actuator through the branch passage isutilized as the high pressure fluid; the actuator and the movable memberare disposed adjacent to each other so that one end of the secondsuction port is connected to the high pressure chamber of the actuator;and the working fluid supplied to the actuator as the high pressurefluid is supplied through the second suction port provided in themovable member to the suction-side space of the first fluid mechanism.16. The expander according to claim 12, wherein the actuator comprises:a cylinder for driving the movable member; a piston for driving themovable member, the piston forming a pressure chamber between the pistonand the cylinder for driving the movable member and rotating the movablemember by swinging eccentrically in the cylinder for driving the movablemember; and a partition member for driving the movable member, thatpartitions the pressure chamber into a high pressure chamber in whichthe high pressure fluid flows, and a low pressure chamber in which thelow pressure fluid flows.
 17. The expander according to claim 16,wherein: the movable member is in a substantially disk-shapedconfiguration; one of main surfaces of the movable member closes thecylinder of the first expansion mechanism while the other one of themain surfaces closes the cylinder for driving the movable member; and onthe other one of the main surfaces side, the movable member is coupledor united with the piston for driving the movable member or an eccentricportion disposed in the piston for driving the movable member.
 18. Theexpander according to claim 16, further comprising a stopper provided onan inner circumferential surface of the cylinder for driving the movablemember and having a protruding shape toward the central axis line of theshaft, for restricting a movable range of the piston for driving themovable member in the cylinder for driving the movable member.
 19. Theexpander according to claim 16, further comprising pushing means forpushing the movable member in a predetermined direction of rotation. 20.The expander according to claim 19, wherein: the pushing means isconfigured to vary the magnitude of the rotational force imparted to themovable member according to the position taken by the movable memberaround the central axis line of the shaft; and the position of themovable member around the central axis line of the shaft is controlledby counterbalancing a rotational force in a forward direction, impartedto the piston for driving the movable member by the pressure differencebetween the high pressure fluid and the low pressure fluid, and arotational force in a reverse direction, imparted to the movable memberby the pushing means.
 21. An expander-compressor unit comprising: anexpander section comprising an expander according to claim 12; and acompressor section integrally coupled to the expander section by theshaft.
 22. A heat pump comprising an expander according to claim
 12. 23.The heat pump according to claim 22, further comprising a pressureregulator for regulating a pressure difference between the high pressurefluid and the low pressure fluid to be supplied to the actuator.
 24. Theheat pump according to claim 23, wherein the pressure regulator acquiresa portion of the working fluid to be sent to the first suction port anddecompresses the acquired working fluid to produce a low pressure fluid,and by adjusting the degree of the decompression, the pressure regulatorcontrols the position of the second suction port around the central axisline of the shaft.
 25. The heat pump according to claim 23, furthercomprising: a first pressure pipe having one end connected to a mainpipe for sending the working fluid to the first suction port and anotherend connected to the pressure regulator and supplying a portion of ahigh pressure working fluid to be expanded to a first chamber of thepressure regulator; and a second pressure pipe having one end connectedto a second chamber of the pressure regulator and another end connectedto the actuator and supplying, to the low pressure chamber of theactuator, the working fluid that has been decompressed to a low pressureby the pressure regulator.